1. Field of the Invention
This invention relates to a pipe coupler in which a plug is selectively connected to or disconnected from a socket in a one-touch operation of the sleeve.
2. Description of the Prior Art
Japanese Examined Utility Model Application Publication No. 57-49030 published on Oct. 27, 1982 discloses a pipe coupler comprising a socket body provided with locking balls, a sleeve urged forward by a spring wound around the socket body and a plug formed with a locking-ball receiving groove. In coupling operation, the plug is connected to a socket constituted by the socket body and the sleeve, via the locking balls, by retracting the sleeve and inserting the plug into the socket. Uncoupling is accomplished also by retracting the sleeve and pulling the plug out of the socket. Coupling and uncoupling are carried out in so-called "a one-touch operation".
In this conventional one-touch operation type pipe coupler, a reciprocating ring urged forward by the spring is provided in the socket body. The ring is moved forward by the spring in a state in which the plug is not connected to the socket, and the outer peripheral surface of the ring receives the locking balls such that the inside portion of each locking ball is prevented from being pushed into the socket body and the outside portion of each locking ball projects outward from the socket body, thereby preventing the sleeve from advancing. On the other hand, as the plug is inserted into the socket, the forward end of the plug retracts the ring and the locking balls are allowed to enter the socket body. When the locking-ball receiving groove in the plug coincides with the locking balls, they are pushed by the sleeve in such a way that the inside portion of each locking ball engages the locking-ball receiving groove in the plug. In consequence, the sleeve advances under the urging force of the spring, and the locking-ball pressing face formed on the inner peripheral surface of the sleeve is pressed against the locking balls, thus preventing the locking balls from being disengaged from the locking-ball receiving groove.
Since the ring and the spring for urging the ring forward are provided in the socket member of a conventional one-touch type pipe coupler, the components of the pipe coupler must be made very thin in order to make the pipe coupler compact or very large in order to prevent flow loss. However, very thin components are poor in durability and cannot be manufactured easily. When, on the other hand, very large components are used, their manufacturing cost is high and they cannot be handled readily. In particular, in a pipe coupler of a small diameter, it is almost impossible to use either very thin components or very large components.